Choose a bilge pump by the job it must do, the boat's electrical system and the discharge installation. Keep the exact pump model and installation manual beside your shopping list.
Build your replacement checklist
- Record the old pump's full model, voltage, outlet size, footprint and control arrangement.
- Measure vertical lift to the discharge, hose length, internal diameter and the available mounting space.
- Compare the candidate's published performance at your installation's lift, not just the largest GPH number on the box.
- Confirm the prescribed hose, fuse, wire sizing and control instructions before ordering.
- Plan access for cleaning, testing and replacement. Record which switch or sensor starts the pump.
A pump sold as a replacement cartridge must match the existing pump family. A similar appearance or GPH label does not establish fit.
Automatic pump or separate float switch?
Separate the pump from the control decision. A non-automatic pump needs the appropriate switching arrangement. Automatic designs vary: some use a water sensor, and others operate differently. Read the exact model's operating description before selecting a replacement switch.
| Question | What to confirm |
|---|---|
| 12V or 24V? | Match the vessel circuit and exact pump rating. |
| External switch? | Identify the existing switch model and the manufacturer's approved arrangement. |
| Replacement cartridge? | Match pump series and part number. |
| Higher advertised capacity? | Check installed output, outlet, electrical requirements and mounting fit. |
Rule LoPro troubleshooting: model-specific checks
Xylem identifies a blocked discharge vent as a cause of slow LoPro priming. With power disconnected, inspect and clear that vent using the manufacturer's procedure, then refit and test.
LoPro's cartridge has low and high sensing positions. Xylem gives approximate activation levels of 1.3 inches and 2 inches respectively. Use its instructions to decide whether changing the position suits the installation.
Xylem permits the LoPro check valve with the straight fitting and warns against combining it with the 90-degree fitting because of back pressure. These details apply to LoPro; they are not universal pump instructions.
Record the symptom before buying parts
- No operation: record whether manual and automatic modes both fail; have the specified electrical checks performed.
- Motor runs with little discharge: record water level and visible hose restrictions, then use the model's priming and discharge checks.
- Repeated cycling: record when the cycle occurs and the sensor or switch type.
Do not bypass protection or increase the fuse rating to make a fault disappear. If water is entering faster than it can be removed, treat that as an immediate safety problem; shopping for a larger pump is not the emergency response.
Find matching equipment
Shop bilge pumpsShop pump switchesShop replacement cartridgesUpdated October 2026. This guide explains selection and planning; use the exact equipment instructions for installation.